Gas Exchange Flashcards
Diffusion of co2 in a plant
Mesophyll cells photosynthesise and this reduces the conc of co2
Co2 diffuses from the air spaces into the cells
This reduces the co2 conc in the air spaces causing more co2 to move into the air spaces from outside the leaf through the stomata
Diffusion of o2 in a plant
Mesophyll cells produce o2 in photosynthesis
O2 diffuses into air spaces from cells
Increases the conc of o2 in the air spaces causing o2 to move from the air spaces to outside the leaf through the stomata
What is a xerophytic plant
A plant which lives in a dry environment so has adaptations to reduce water loss
Adaptations of xerophytic plants
Reduced number of stomata so less surface area for water loss
Hairs to trap water vapour so reduced conc gradient
Thick waxy cuticles so increased diffusion distance
How do insects limit water loss?
Exoskeleton is covered with a waterproof cuticle made from chitin
Small surface area to volume ratio to minimise area over which water is lost
Movement of oxygen through the insect
Oxygen enters the insect through spiracles and moves into the trachea, the spiracle closes
Oxygen diffuses through the trachea into the tracheoles
Oxygen is delivered directly into respiring tissues
Insect adaptations for gas exchange
Tracheoles - Thin walls - Short diffusion distance
Also highly branched so large surface area for gas exchange
Body pumping - Active process which maintains conc gradient for o2 and co2. High conc at the ends of the tracheoles compared to spiracle ends draws more oxygen in
Lactate - Produced in muscle cells, lowers water potential of muscle cells so water moves in via osmosis from the tracheoles to the muscle cells and draws air into the tracheoles with the water
Adaptations in fish for gas exchange
Lamelle - on each filament increasing S.A
Gill filaments - Thin and lots of them again increasing S.A
Rich network of capillaries surrounding lamelle - increase concentration gradient
Gas exchange in fish
- Water containing oxygen enters the fish’s mouth, passes through the lamelle on the gill filaments where most of the oxygen is removed
- The water containing little oxygen then leaves through the gill opening
Counter current flow
Position of filament and lamallae means that blood and water flow in opposite directions- massively increasing fish’s ability to absorb oxygen from the water as a diffusion gradient is always maintained
What is a tissue
A group of cells that work together to perform a particular function
What is an organ
Groups of distinct tissues which work towards on a particular function
